linux-kernel - Re: [PATCH 1/8] KVM: SVM: Fix nested nmi handling

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Date:	Fri, 23 Apr 2010 16:42:52 +0200
From:	Alexander Graf <agraf@...e.de>
To:	Joerg Roedel <joerg.roedel@....com>
Cc:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/8] KVM: SVM: Fix nested nmi handling


On 23.04.2010, at 16:31, Joerg Roedel wrote:

> On Fri, Apr 23, 2010 at 04:24:54PM +0200, Alexander Graf wrote:
>> 
>> On 23.04.2010, at 16:22, Joerg Roedel wrote:
> 
>>> No, nested_svm_nmi runs in atomic context where we can't emulate a
>>> vmexit. We set exit_required and emulate the vmexit later.
>> 
>> So we modify the L2 rflags and then trigger a #vmexit, leaving the l2
>> state broken?
> 
> No, the rflags are changed in enable_nmi_window which isn't called when
> we run nested and the nested hypervisor intercepts nmi. So it only runs
> in the !nested case where it can't corrupt L2 state.

Last time I checked the code enable_nmi_window was the function triggering the #vmexit, so it should run in that exact scenario. If what you say is true, where do we #vmexit instead then?


Alex

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